The weather service in Buffalo, which typically doesn't look more than a week out, included an unusual warning in its detailed forecast discussion this morning.

"After about December 10th-12th, there are increasing signals in long-range ensemble guidance that several blasts of true arctic air may be in play for the Great Lakes and Northeast. Obviously details are impossible to predict at this time range, but the large-scale pattern suggests the possibility of numerous high-impact lake effect snow events during the 8-14 day period taking us into mid December. Stay tuned."

The arrival of the Arctic air will spell an end to a long stretch of relatively mild weather. Both September and October were well above-average temperature-wise, with October finishing as the fifth-warmest on record in Rochester.

November wound up exactly average in terms of temperature, though it featured plenty of warm days and brought just 2.6 inches of snow.

December is beginning unusually warm, too, with daily highs forecast to be in the 40's through this weekend and the low 50's on Monday and Tuesday.

An arriving cold front — the advance guard of the frigid air mass — is expected to sweep through the region on Wednesday, dropping high temperatures to the 30's and bringing first rain and then snow showers on Thursday.

Based on the current outlook, the full Arctic effect will be felt a few days after that.